1. Field of Invention
The present invention relates to a novel process for preparation of sulfonylurea-based derivatives. Particularly, the present invention relates to a novel process for preparation of sulfonylurea derivatives having the following general formula (I), ##STR2## wherein R.sup.1 represents hydrogen, C.sub.1 -C.sub.4 alkyl or phenyl;
R.sup.2 represents hydrogen, C.sub.1 -C.sub.4 alkyl, allyl or propargyl; and PA1 R.sup.3 represents hydrogen, methyl, ethyl or phenyl, and to an intermediate compound useful for this process and a process for preparing said intermediate compound. PA1 R.sup.1, R.sup.2 and R.sup.3 are as defined above, and PA1 M represents a monovalent metal atom. PA1 R.sup.4 represents hydrogen or benzyl. PA1 R represents C.sub.1 -C.sub.4 alkyl, C.sub.2 -C.sub.4 alkenyl, aralkyl(preferably benzyl) or aryl(preferably phenyl).
2. Background Art
The sulfonylurea derivative of formula (I) above is a known herbicide compound and processes for preparing the same are disclosed in numerous publications. For example, European Early Published Patent No. 87,780 discloses the three methods for preparing the compound (I), in which the first method comprises reacting an isocyanate of formula (II) with an amine compound of formula (VII); the second method comprises reacting an amine of formula (III) with an isocyanate of formula (VI); and the third method comprises reacting a carbamate of formula (IV) with an amine compound of formula (VII): ##STR3## wherein R.sup.1, R.sup.2 and R.sup.3 are as defined above
Both the first and second method as described above are the general method for preparing sulfonylurea derivatives by synthesizing and separating isocyanates which are then reacted with amines. However, the isocyanate used as the starting material in these methods is synthesized by reacting the amine derivative of formula (III) or (VII) with a poisonous substance, phosgene. Accordingly, such methods using the isocyanate have some disadvantages in that mass use of phosgene in the industrial scale requires a special safety equipment, hydrochloric acid produced as by-product should be treated and the remaining phosgene should be recovered. Further, when the compound of formula (I) is prepared by reacting such isocyanate compound with the amine derivative, the yield of the desired product (I) is as low as 70 to 80%.
Moreover, as shown in the following reaction scheme, the first method produces the sulfonylurea derivative of formula (I) starting from the sulfonylchloride of formula (V) via the isocyanate of formula (II) according to a complicated multi-step procedure. Accordingly, this first method is disadvantageous in application to the mass production in the industrial scale. ##STR4##
In addition, the third method as described above is a method identical to the method described in Japanese Laying-open Patent Publication No. (Hei) 03-200742 which requires a stringent reaction condition including high reaction temperature and produces the desired product (I) in a low yield. Therefore, this method is also unsuitable to the industrial scale production.
Thus, the present inventors have extensively studied to find out a method which can conveniently prepare the desired compound of formula (I) in a simple manner. As a result we have identified a novel single-step method capable of preparing the desired compound (I) in a high purity and in a high yield.
Therefore, it is an object of the present invention to provide a novel process for preparing the sulfonylurea derivative having the general formula (I) as defined above.
It is a further object of the present invention to provide a novel process for preparing an intermediate sulfonylchloride compound having the general formula (V) as defined above.
It is another object of the present invention to provide a novel intermediate compound having the general formula (VIII), as defined below, which can be used in the process for preparing the desired compound (I) according to the present invention.
Further, it is still another object of the present invention to provide a process for preparing the novel intermediate compound of formula (VIII).
The more pertinent and important features of the present invention have been outlined above in order that the detailed description of the invention which follows will be better understood and that the present contribution to the art can be fully appreciated. Those skilled in the art can appreciate that the conception and the specific embodiment disclosed herein may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Further, those skilled in the art can realize that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the claims.